Biodiversity is an expression that is used to refer to biological diversity, which is actually a habitat in which it has been shown that there is one or several particular classes of living beings and in this article we are going to deal with the features of biodiversity.
What is Biodiversity?
The term is related to the many elements and variables that organic beings have. The concept of biodiversity can be understood from several levels, be it from the taxonomic, functional, phylogenetic, genetic or trophic level and all of them are part of the characteristics of biodiversity.
An area that is inhabited by a single species that is early in age, but to the point of evolutionary view, by specimens that are genetically homogeneous that have dispersed over small geographic areas and a narrow range of habitat, is said to be It is an ecosystem that has low intensity biodiversity.
The notion of a biodiversity means that an area contains different species, as well as their biological variation, within an area. By contrast, a habitat that has several species, some of which may be ancient, others whose specialization process has been verified recently, which has genetic material that is heterogeneous and has a wide distribution, would be a region that It has a high diversity.
However, the reference to low or high biodiversity is relative terms. For this reason, there are several indices and parameters through which the diversity of an area can be quantified, such as the Shannon or Simpson index, among others. If we base ourselves on them, we will observe that the distribution of living beings is not homogeneous in the world.
What is part of the characteristics of biodiversity is that a greater index of diversity can be found the closer we get to the tropical regions. The characteristics of biodiversity they can be studied using two disciplines that are complementary to each other, ecology and evolutionary biology. The supporters of ecology focus especially on the factors that influence local diversity and that act in short periods of time.
While evolutionary biologists, on the other hand, focus on higher time scales and focus on the events that have produced an extinction, the generation of adaptations, and speciation, among others.
What has been shown is that in the last 50 years, the presence of human beings, global warming, and various factors have been capable of altering the distribution and diversity of a significant number of species. Knowledge and quantification of the characteristics of biodiversity are essential elements for formulating hypotheses to solve the observed problems.
Definition of Biodiversity
The first researcher to use the term biodiversity in the ecological literature was E. O Wilson, in 1988. However, the notion of biological diversity has been in development since the XNUMXth century, and continues to be widely used today. . Biodiversity refers to the diversity of life forms. It extends to all levels of organization of matter, and it is possible that it is classified from an evolutionary or functional ecological point of view.
That is, diversity cannot only be understood in terms of the number of species. The variability observed at other taxonomic and environmental levels also exerts an influence, as we will explain in future sections of this post.
The characteristics of biodiversity have been the subject of studies since the time of Aristotle. The curiosity to study the origin of life and the need to determine an order led philosophers to study the different forms of life and to establish arbitrary classification systems. In this way they were born in the sciences of systematics and taxonomy, and therefore, the analysis of diversity.
Types of biodiversity
As for Types of Biodiversity, there are many characteristics of biodiversity and we are going to refer to each one of them in separate sections, to know What are the characteristics of biodiversity?
genetic diversity
Biological diversity can be studied at different scales, starting with genetics. An organism is made up of thousands of genes grouped in its DNA, which is packaged inside the cells.
The different ways that a gene can be found, which are known as alleles, and the diversifications in the chromosomes between individuals make up the genetic diversity. A small population, which has a homogeneous genome among its members, is somewhat diverse.
The genetic variation that can be found between individuals belonging to the same species can be the effect of a number of processes such as recombinations, gene pool isolation, mutations, gradients, local selective pressures, among other phenomena.
Differentiation becomes the basis for evolution and for the birth of adaptations. A variable population may be the product of changes in environmental conditions, but little change may be due to population decline, or in some extreme cases cause local extinction of a species.
Likewise, being able to have knowledge of the degree of genetic modification of a population of individuals is essential if effective species conservation plans are to be implemented, since this parameter affects the resilience and persistence of the species.
individual diversity
At this level of organization of matter, we can find variation in terms of anatomy, physiology, and behavior in individual organisms.
Population diversity
In biology, populations are defined as a set of individuals that are part of the same species that coexist in time and space, and that can potentially reproduce.
If we talk about a population level, the genetic modification of the individuals that make up said population, puts its grain of sand so that biodiversity exists and, again, constitutes the basis for an adaptive evolution to take place. A specific example of this is the human population itself, in which all individuals exhibit observable phenotypic variation.
Species that have not had genetic variation and have uniform populations are more inclined towards extinction, both due to causes that come from the environment, and those that have been caused by the activity of human beings.
Diversity at the species level
If we go ascending in the level of organization of matter, it is possible to analyze the characteristics of biodiversity in terms of species. Biodiversity is a common object of study by ecologists and conservation biologists at this level.
Diversity above the species level
Biodiversity characteristics can continue to be analyzed above the species level. This is, taking into consideration other levels of taxonomic classification such as genera, families, orders, and others. However, this is more common in studies that are linked to paleontology.
Thus, it is possible to go up in scale, to obtain the meaning of biodiversity, until we can achieve the comparisons made by biogeography, which is nothing more than the recognition of a wealth of differences between species in large geographic regions.
How is biodiversity measured?
In the case of biologists, what is relevant is having parameters that facilitate the quantification of biodiversity. To consider this work completed, there are different methodologies, it can even be measured from a theoretical or functional point of view.
Functional measurement scales contain genetic, species, and ecosystem diversity, from lowest to highest. The theoretical point of view is based on alpha, beta and gamma diversity. In the same way, a community can be evaluated, through the description of its physical attributes.
It is usual to use statistical indices with which the diversity of species can be measured. These take two important measures, which are the total number of species in the sample and the relative abundance of them. Next, we will describe the measures and indices that are most used by ecologists.
Alpha, beta and gamma diversity
Alpha, beta and gamma diversity are the three diversity scales that are recognized by the IUCN, which stands for the International Union for Conservation of Nature. This point of view was proposed by plant ecologist Robert Harding Whittaker in the 1960s and is still valid today.
Alpha diversity is the term used to designate species at the local level, that is, within a habitat or ecological community. Beta is the difference in species composition between communities. Finally, gamma is the number of species at the regional level.
However, this division generates an inconvenience when it comes to defining the local area and how a region should be objectively delimited, beyond mere political limits that biologically have no significance. The raising of these limits is influenced by the study question and by the group involved, due to which the previous questions cannot have an obvious answer.
In most ecological research dealing with biodiversity features, importance is placed on alpha diversity. Next we will explain some examples of biodiversity.
alpha diversity
Alpha diversity is usually exposed in species richness and species evenness requirements. During a sampling carried out, the area or the zone that the scientist chooses represents an entire community. Therefore, making a list of the number and name of the species that inhabit it is the first step to be able to measure the characteristics of the biodiversity of an area.
The number of species found within a community or area is the species richness. When this data is known, other elements must be studied, such as, for example, taxonomic uniqueness, taxonomic diversity, ecological significance, and interactions between species, among others.
Usually, the richness of species, and biodiversity in general, increase as the area we are studying expands or when we move from greater to lesser longitude and latitude towards the equator.
It must be taken into consideration that not all species help in the same way for diversity to exist in the area. From an ecological perspective, the different dimensions of biodiversity are represented by the number of trophic levels and the variety of life cycles that contribute in a differentiated way.
The existence of some species in the area has the capacity to increase the level of diversity of an ecological community, while that of others does not.
beta diversity
Beta diversity is a measure of the diversity that is captured between communities. It is a measure of the range and degree of change in species across a gradient or from one habitat to another. One of the activities of this type of measurement is to study the comparison of diversity on the slope of a mountain. Beta diversity also takes into account the temporal change in species composition.
gamma diversity
Gamma diversity is the one whose function is to quantify diversity at a higher spatial level. It is the one that deals with explaining the diversity of species within a wide geographic range. Usually it turns out to be that of the alpha diversity and the degree of beta differentiation between them.
In this way, gamma diversity turns out to be the rate at which additional species are found and their geographic substitution is studied.
Species diversity indices
In ecology, diversity indices are widely used, in order to quantify it using mathematical variables.
A diversity index is conceptualized as a statistical summary that is used to measure the total number of local species living in different habitats. The index can be represented as a dominance or as an equity and we are going to talk about the most used ones.
Shannon Diversity Index
The Shannon index, or Shannon-Weaver index, is commonly used to measure specific biodiversity. It is represented by an H', and the index values range only between positive numbers. In most ecosystems the indices are valued between 2 to 4.
Values below 2 are considered to have relatively little diversity, as is the case of desert ecosystem. On the other hand, values greater than 3 indicate the existence of a high level of diversity, as is the case of the forest or Tropical climate or a reef.
In order to calculate the value of this index, the number of species is considered, which is what we call richness, and their relative number, which we call abundance. The maximum value of the index is usually close to 5 and the minimum value is 0, which is the place where only species exist, which means that there is no diversity. An ecosystem with a Shannon index of 0 may be a monoculture.
Simpson diversity index
Simpson's index is the one represented by a letter D, and it estimates the probability that two individuals chosen at random from a sample belong to the same species, or to another taxonomic category.
In the same way, the Simpson diversity index is expressed as 1 – D. Then the values are between 0 and 1 and, inverse to the previous index, it expresses the probability that two randomly chosen individuals form part of different species.
Another way to state it is by means of a reciprocal index that is represented as 1/D. In this way, the value of 1 expresses the existence of a community that has only one species. If the value increases, it is an indication that there is greater diversity.
Although the Shannon and Simpson indexes are the most commonly used in the ecological literature, there are others such as the Margalef, McIntosh, and Pielou index, among others.
Why should we quantify biodiversity?
Biodiversity measurements are essential if you intend to have data on fluctuations in diversity, according to changes in the environment that damage ecosystems, whether caused naturally or by the action of human beings. .
The reason for measuring biodiversity is to verify the consequences of the evolution of life on Earth, which began around 3.5 billion years ago and during all that time, living beings have given rise to different forms of life. that are observed on the planet today.
Therefore, the different processes of evolution have been responsible for this enormous number of living beings, thanks to the liberation of competition, ecological divergence and co-evolution.
